Update AudioRenderer API to fire changes in BufferingState.

media/filters/audio_renderer_impl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Audio rendering unit utilizing an AudioRendererSink to output data.
 //
 // This class lives inside three threads during it's lifetime, namely:
 // 1. Render thread
 //    Where the object is created.
 // 2. Media thread (provided via constructor)
@@ skipping 50 matching lines @@
       AudioRendererSink* sink,
       ScopedVector<AudioDecoder> decoders,
       const SetDecryptorReadyCB& set_decryptor_ready_cb,
       AudioHardwareConfig* hardware_params);
   virtual ~AudioRendererImpl();
 
   // AudioRenderer implementation.
   virtual void Initialize(DemuxerStream* stream,
                           const PipelineStatusCB& init_cb,
                           const StatisticsCB& statistics_cb,
-                          const base::Closure& underflow_cb,
                           const TimeCB& time_cb,
+                          const BufferingStateCB& buffering_state_cb,
                           const base::Closure& ended_cb,
                           const PipelineStatusCB& error_cb) OVERRIDE;
   virtual void StartRendering() OVERRIDE;
   virtual void StopRendering() OVERRIDE;
   virtual void Flush(const base::Closure& callback) OVERRIDE;
   virtual void Stop(const base::Closure& callback) OVERRIDE;
   virtual void SetPlaybackRate(float rate) OVERRIDE;
-  virtual void Preroll(base::TimeDelta time,
-                       const PipelineStatusCB& cb) OVERRIDE;
-  virtual void ResumeAfterUnderflow() OVERRIDE;
+  virtual void StartPlayingFrom(base::TimeDelta timestamp) OVERRIDE;
   virtual void SetVolume(float volume) OVERRIDE;
 
-  // Disables underflow support.  When used, |state_| will never transition to
-  // kUnderflow resulting in Render calls that underflow returning 0 frames
-  // instead of some number of silence frames.  Must be called prior to
-  // Initialize().
-  void DisableUnderflowForTesting();
-
   // Allows injection of a custom time callback for non-realtime testing.
   typedef base::Callback<base::TimeTicks()> NowCB;
   void set_now_cb_for_testing(const NowCB& now_cb) {
     now_cb_ = now_cb;
   }
 
  private:
   friend class AudioRendererImplTest;
 
   // Important detail: being in kPlaying doesn't imply that audio is being
   // rendered. Rather, it means that the renderer is ready to go. The actual
   // rendering of audio is controlled via Start/StopRendering().
   //
   //   kUninitialized
   //         | Initialize()
   //         |
   //         V
   //    kInitializing
   //         | Decoders initialized
   //         |
   //         V            Decoders reset
   //      kFlushed <------------------ kFlushing
-  //         | Preroll()                  ^
+  //         | StartPlayingFrom()         ^
   //         |                            |
-  //         V                            | Flush()
-  //     kPrerolling ----------------> kPlaying ---------.
-  //           Enough data buffered       ^              | Not enough data
-  //                                      |              | buffered
-  //                 Enough data buffered |              V
-  //                                 kRebuffering <--- kUnderflow
-  //                                      ResumeAfterUnderflow()
+  //         |                            | Flush()
+  //         `---------> kPlaying --------'

[acolwell GONE FROM CHROMIUM, 2014/05/13 20:44:27]

\o/ so much nicer

   enum State {
     kUninitialized,
     kInitializing,
     kFlushing,
     kFlushed,
-    kPrerolling,
     kPlaying,
     kStopped,
-    kUnderflow,
-    kRebuffering,
   };
 
   // Callback from the audio decoder delivering decoded audio samples.
   void DecodedAudioReady(AudioBufferStream::Status status,
                          const scoped_refptr<AudioBuffer>& buffer);
 
   // Handles buffers that come out of |splicer_|.
   // Returns true if more buffers are needed.
   bool HandleSplicerBuffer(const scoped_refptr<AudioBuffer>& buffer);
 
@@ skipping 34 matching lines @@
 
   // Helper methods that schedule an asynchronous read from the decoder as long
   // as there isn't a pending read.
   //
   // Must be called on |task_runner_|.
   void AttemptRead();
   void AttemptRead_Locked();
   bool CanRead_Locked();
   void ChangeState_Locked(State new_state);
 
-  // Returns true if the data in the buffer is all before
-  // |preroll_timestamp_|. This can only return true while
-  // in the kPrerolling state.
-  bool IsBeforePrerollTime(const scoped_refptr<AudioBuffer>& buffer);
+  // Returns true if the data in the buffer is all before |start_timestamp_|.
+  // This can only return true while in the kPlaying state.
+  bool IsBeforeStartTime(const scoped_refptr<AudioBuffer>& buffer);
 
   // Called upon AudioBufferStream initialization, or failure thereof (indicated
   // by the value of |success|).
   void OnAudioBufferStreamInitialized(bool succes);
 
   // Used to initiate the flush operation once all pending reads have
   // completed.
   void DoFlush_Locked();
 
   // Calls |decoder_|.Reset() and arranges for ResetDecoderDone() to get
@@ skipping 25 matching lines @@
   AudioBufferStream audio_buffer_stream_;
 
   // Interface to the hardware audio params.
   const AudioHardwareConfig* const hardware_config_;
 
   // Cached copy of hardware params from |hardware_config_|.
   AudioParameters audio_parameters_;
 
   // Callbacks provided during Initialize().
   PipelineStatusCB init_cb_;
-  base::Closure underflow_cb_;
   TimeCB time_cb_;
+  BufferingStateCB buffering_state_cb_;
   base::Closure ended_cb_;
   PipelineStatusCB error_cb_;
 
+  BufferingState buffering_state_;
+
   // Callback provided to Flush().
   base::Closure flush_cb_;
 
-  // Callback provided to Preroll().
-  PipelineStatusCB preroll_cb_;
-
   // Typically calls base::TimeTicks::Now() but can be overridden by a test.
   NowCB now_cb_;
 
   // After Initialize() has completed, all variables below must be accessed
   // under |lock_|. ------------------------------------------------------------
   base::Lock lock_;
 
   // Algorithm for scaling audio.
   scoped_ptr<AudioRendererAlgorithm> algorithm_;
 
   // Simple state tracking variable.
   State state_;
 
   // Keep track of whether or not the sink is playing and whether we should be
   // rendering.
   bool rendering_;
   bool sink_playing_;
 
   // Keep track of our outstanding read to |decoder_|.
   bool pending_read_;
 
   // Keeps track of whether we received and rendered the end of stream buffer.
   bool received_end_of_stream_;
   bool rendered_end_of_stream_;
 
   scoped_ptr<AudioClock> audio_clock_;
 
-  base::TimeDelta preroll_timestamp_;
+  base::TimeDelta start_timestamp_;
 
   // We're supposed to know amount of audio data OS or hardware buffered, but
   // that is not always so -- on my Linux box
   // AudioBuffersState::hardware_delay_bytes never reaches 0.
   //
   // As a result we cannot use it to find when stream ends. If we just ignore
   // buffered data we will notify host that stream ended before it is actually
   // did so, I've seen it done ~140ms too early when playing ~150ms file.
   //
   // Instead of trying to invent OS-specific solution for each and every OS we
   // are supporting, use simple workaround: every time we fill the buffer we
   // remember when it should stop playing, and do not assume that buffer is
   // empty till that time. Workaround is not bulletproof, as we don't exactly
   // know when that particular data would start playing, but it is much better
   // than nothing.
   base::TimeTicks earliest_end_time_;
   size_t total_frames_filled_;
 
-  bool underflow_disabled_;
-
-  // True if the renderer receives a buffer with kAborted status during preroll,
-  // false otherwise. This flag is cleared on the next Preroll() call.
-  bool preroll_aborted_;
-
   // End variables which must be accessed under |lock_|. ----------------------
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<AudioRendererImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioRendererImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_AUDIO_RENDERER_IMPL_H_